Contribution of tiller age category to herbage accumulation of Marandu palisadegrass under two fertilization regimes

Abstract

Based on the hypothesis that climate and fertilizers influence the proportion of tiller age categories in the canopy and, consequently, in herbage accumulation, the objective of this study was to determine the population density and the contribution of tiller age categories for herbage accumulation of Urochloa brizantha cv. Marandu during the year and in response to phosphate and nitrogen fertilization. The treatments consisted of two fertilization strategies: low and high fertilization and three tiller ages (young, mature and old), evaluated at four times of the year: winter, early and late spring, and summer. The total number of tillers and the proportion of young tillers were higher in late spring and summer. The growth and herbage accumulation rates showed a typical seasonal pattern and were higher in the canopy under high fertilization. Old tillers contributed more to control the total stem growth rate, as well as the canopy senescence rate. The highest percentage of young tillers is related to the high herbage accumulation in the Marandu palisadegrass canopy.

Current Scenario and Perspectives for Nitrogen Fertilization Strategies on Tropical Perennial Grass Pastures: A Review

“…The current fertilization practices recommend a wide range on annual rates, varying from 50 kg N ha −1 up to 500 kg N ha −1 for non-irrigated pastures [46][47][48]. Despite it being recommended that annual fertilization amounts follow an installment protocol, the N rate per application aiming at strategic fertilization remains uncertain.…”

“…The beginning of the wet season is characterized by returning favorable growth conditions when precipitation events are more evenly distributed [22]. In this period, in well managed monospecific swards of tropical perennial grasses, tiller population undergo to a strong renewal process, characterized by intense tiller mortality, predominantly those plants that survived from the dry season, associated with high rates of tiller appearance [47]. As a result of this process, the profile of the population is characterized by the predominance of young tillers, which are highly responsive to soil N availability [47,57].…”

“…In regularly managed pastures, the process is part of a natural cycle of tiller population dynamics, and occurs regardless of the grazing method [58,59]. Demand for N by plants is higher during the beginning of the growing season [56] due to the intense tiller population renewal, high proportion of young tillers, and fast leaf turnover [47,60]. However, with the onset of the rainy season and soil rewetting, microbial and soil fauna activity are enhanced [61], and then, litter breakdown and decomposition may substantially contribute to N release [62].…”